Elbow dislocations involving fractures of the coronoid process of the ulna and/or the radial head have a grave prognosis. The specific aim of this research project is-to investigate the respective contributions of the coronoid process and radial head to stability of the elbow joint in a model simulating a fracture-dislocation of the elbow. This study will also assess a role of the radial head endoprosthesis in the context of elbow instability. A cadaveric model of an elbow fracture- dislocation has been developed to simulate the soft tissue and bony damage resulting from such an injury. Simulated muscle loading will be applied while the joint will be moved passively through its full range of motion in the sagittal plane. The kinematics of the elbow joint motion will be studied, with particular attention to subluxation and dislocation of the joint. The three-dimensional spatial orientation of the ulna relative to the humerus will be measured using an electromagnetic tracking device. The kinematics of the intact elbow joint will be first assessed, then the soft-tissues will be divided to model a simple dislocation, and then the coronoid process will be resected in a step-wise fashion. Each of the testing conditions will be repeated with the radial head resected as well as with the radial head reattached using a plate and screws to simulate the condition of an intact radial head. Each of the testing conditions will also be repeated with the already implanted radial head endoprostheses with a mobile and immobile head. The assessment of the size of coronoid fractures, the significance of radial head fractures and the role of the radial head endoprosthesis with regard to recurrent and chronic subluxation or dislocation in the context of elbow fracture-dislocations has important clinical relevance. Recurrent and chronic subluxation or dislocation following treatment of elbow fracture-dislocations is an extremely poor prognostic factor. This study will identify patterns of bony injury that lead to potential elbow instability in the context of an elbow fracture dislocation. This will be helpful to assess the relative efficacy of specific treatment options including treatment of fractures, prosthetic replacement of the radial head and collateral ligament repair or reconstruction.